Back to EveryPatent.com
United States Patent |
5,580,540
|
Nakagawa
|
December 3, 1996
|
Zeolite SSZ-44
Abstract
The present invention relates to new crystalline zeolite SSZ-44 prepared by
processes for preparing crystalline molecular sieves, particularly large
pore zeolites, using a N,N-diethyl-cis-2,6-dimethyl piperidinium cation
templating agent.
Inventors:
|
Nakagawa; Yumi (Oakland, CA)
|
Assignee:
|
Chevron U.S.A. Inc. (San Francisco, CA)
|
Appl. No.:
|
566201 |
Filed:
|
December 1, 1995 |
Current U.S. Class: |
423/718; 423/706; 423/713 |
Intern'l Class: |
C01B 039/46 |
Field of Search: |
423/718,713
|
References Cited
U.S. Patent Documents
4076842 | Feb., 1978 | Plank et al. | 423/718.
|
4229424 | Oct., 1980 | Kokotailo | 423/718.
|
4705674 | Nov., 1987 | Araya et al. | 423/718.
|
4837000 | Jun., 1989 | Takatsu et al. | 423/718.
|
5332566 | Jul., 1994 | Moini | 423/718.
|
5512267 | Apr., 1996 | Davis et al. | 423/718.
|
Other References
Zones, S. I., et al., Zeolites: Facts, Figures, Future, 1988, pp. 299-309.
(No Month).
Barrer, R. M., Hydrothermal Chemistry of Zeolites, 1982, pp. 157-162.(No
Month).
Barrer, R. M. and Denny, P. J., J. Chem. Soc., 1961, pp. 971-982.(No Month)
.
|
Primary Examiner: Bell; Mark L.
Assistant Examiner: Sample; David
Attorney, Agent or Firm: Sheridan; R. J.
Claims
What is claimed is:
1. A zeolite having an average pore size greater than about 6 Angstroms and
having the X-ray diffraction lines of Table I.
2. A zeolite having a mole ratio greater than about 20 of an oxide of a
first tetravalent element to an oxide of a second trivalent or tetravalent
element which is different from said first tetravalent element, and having
the X-ray diffraction lines of Table I.
3. A zeolite having a mole ratio greater than about 20 of an oxide selected
from the group consisting of silicon oxide, germanium oxide and mixtures
thereof to an oxide selected from aluminum oxide, gallium oxide, iron
oxide, boron oxide, titanium oxide, indium oxide, vanadium oxide and
mixtures thereof, and having the X-ray diffraction lines of Table I.
4. A zeolite according to claim 3 wherein the oxides comprise silicon oxide
and aluminum oxide.
5. A zeolite according to claim 3 wherein the oxides comprise silicon oxide
and boron oxide.
6. A zeolite according to claim 3 wherein the oxides comprise silicon oxide
and titanium oxide.
7. A zeolite having an average pore size greater than about 6 Angstroms and
having, after calcination, the X-ray diffraction lines of Table II.
8. A zeolite according to claim 7, wherein said zeolite is predominantly in
the hydrogen form.
9. A zeolite according to claim 7 made substantially free of acidity by
neutralizing said zeolite with a basic metal.
10. A zeolite having a mole ratio greater than about 20 of an oxide
selected from the group consisting of silicon oxide, germanium oxide and
mixtures thereof to an oxide selected from the group consisting of
aluminum oxide, gallium oxide, iron oxide, boron oxide, titanium oxide,
indium oxide, vanadium oxide and mixtures thereof and having, after
calcination, the X-ray diffraction lines of Table II.
11. A zeolite according to claim 10, wherein said zeolite is predominantly
in the hydrogen form.
12. A zeolite according to claim 10 made substantially free of acidity by
neutralizing said zeolite with a basic metal.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to new crystalline zeolite SSZ-44, a method
for preparing SSZ-44 using a N,N-diethyl-cis-2,6-dimethyl piperidinium
cation templating agent, and processes employing SSZ-44 as a catalyst.
2. State of the Art
In conventional usage the term "molecular sieve" refers to a material
having a fixed, open-network structure, usually crystalline, that may be
used to separate hydrocarbons or other mixtures by selective occlusion of
one or more of the constituents, or may be used as a catalyst in a
catalytic conversion process. The term "zeolite" refers to a molecular
sieve containing a silicate lattice, usually in association with some
aluminum, boron, gallium, iron, and/or titanium. In the following
discussion and throughout this disclosure, the terms molecular sieve and
zeolite will be used more or less interchangeably. One skilled in the art
will recognize that the teachings relating to zeolites are also applicable
to the more general class of materials called molecular sieves.
Natural and synthetic crystalline molecular sieves are useful as catalysts
and adsorbents. Each crystalline molecular sieve is distinguished by a
crystal structure with an ordered pore structure, and is characterized by
a unique X-ray diffraction pattern. Thus, the crystal structure defines
cavities and pores which are characteristic of the different species. The
adsorptive and catalytic properties of each crystalline molecular sieve
are determined in part by the dimensions of its pores and cavities.
Accordingly, the utility of a particular molecular sieve in a particular
application depends at least partly on its crystal structure.
Because of their unique sieving characteristics, as well as their catalytic
properties, crystalline molecular sieves are especially useful in
applications such as hydrocarbon conversion, gas drying and separation.
Although many different crystalline molecular sieves have been disclosed,
there is a continuing need for new zeolites with desirable properties for
gas separation and drying, hydrocarbon and chemical conversions, and other
applications.
Crystalline aluminosilicates are usually prepared from aqueous reaction
mixtures containing alkali or alkaline earth metal oxides, silica, and
alumina. Crystalline borosilicates are usually prepared under similar
reaction conditions except that boron is used in place of aluminum. By
varying the synthesis conditions and the composition of the reaction
mixture, different zeolites can often be formed.
Organic templating agents are believed to play an important role in the
process of molecular sieve crystallization. Organic amines and quaternary
ammonium cations were first used in the synthesis of zeolites in the early
1960s as reported by R. M. Barrer and P. J. Denny in J. Chem. Soc. 1961 at
pages 971-982. This approach led to a significant increase in the number
of new zeolitic structures discovered as well as an expansion in the
boundaries of composition of the resultant crystalline products.
Previously, products with low silica to alumina ratios (SiO.sub.2 /Al.sub.2
O.sub.3 .ltoreq.10) had been obtained, but upon using the organocations as
components in the starting gels, zeolites with increasingly high SiO.sub.2
/Al.sub.2 O.sub.3 were realized. Some of these materials are summarized by
R. M. Barrer 1982, Hydrothermal Chemistry of Zeolites, New York: Academic
Press, Inc.
Unfortunately, the relationship between structure of the organocation and
the resultant zeolite is far from predictable, as evidenced by the
multitude of products which can be obtained using a single quaternary
ammonium salt as reported by S. I. Zones et al., 1989, Zeolites: Facts,
Figures, Future, ed. P. A. Jacobs and R. A. van Santen, pp. 299-309,
Amsterdam: Elsevier Science Publishers, or the multitude of organocations
which can produce a single zeolitic product as reported by R. M. Barrer,
1989, Zeolite Synthesis, ACS Symposium 398, ed. M. L. Occelli and H. E.
Robson, pp. 11-27, American Chemical Society.
Thus, it is known that organocations exert influence on the zeolite
crystallization process in many unpredictable ways. Aside from acting in a
templating role, the organic cation's presence also greatly affects the
characteristics of the gel. These effects can range from modifying the gel
pH to altering the interactions of the various components via changes in
hydration (and thus solubilities of reagents) and other physical
properties of the gel. Accordingly, investigators have now begun to
consider how the presence of a particular quaternary ammonium salt
influences many of these gel characteristics in order to determine more
rigorously how such salts exert their templating effects. In summary, a
variety of templates have been used to synthesize a variety of molecular
sieves, including zeolites of the silicate, aluminosilicate, and
borosilicate families. However, the specific zeolite which may be obtained
by using a given template is at present unpredictable. In particular,
organocation templating agents have been used to prepare many different
combinations of oxides with molecular sieve properties, with silicates,
aluminosilicates, aluminophosphates, borosilicates and
silicoaluminophosphates being well known examples.
SUMMARY OF THE INVENTION
The present invention is directed to a family of crystalline molecular
sieves with unique properties, referred to herein as "zeolite SSZ-44" or
simply "SSZ-44". Preferably SSZ-44 is obtained in its silicate,
aluminosilicate, or borosilicate form. The term "silicate" refers to a
zeolite having a high mole ratio of silicon oxide relative to aluminum
oxide, preferably a mole ratio greater than 100. As used herein the term
"aluminosilicate" refers to a zeolite containing both alumina and silica
and the term "borosilicate" refers to a zeolite containing oxides of both
boron and silicon.
In accordance with the present invention, there is provided a zeolite
having an average pore size greater than about 6 Angstroms and having the
X-ray diffraction lines of Table I.
In accordance with this invention there is also provided a zeolite having a
mole ratio of an oxide of a first tetravalent element to an oxide of a
second trivalent or tetravalent element different from said first
tetravalent element, said mole ratio being greater than about 20 and
having the X-ray diffraction lines of Table I.
Further in accordance with this invention there is provided a zeolite
having a mole ratio of an oxide selected from silicon oxide, germanium
oxide and mixtures thereof to an oxide selected from aluminum oxide,
gallium oxide, iron oxide, boron oxide, titanium oxide, indium oxide,
vanadium oxide and mixtures thereof greater than about 20 and having the
X-ray diffraction lines of Table I below. The present invention further
provides such a zeolite having a composition, as synthesized and in the
anhydrous state, in terms of mole ratios as follows:
YO.sub.2 W.sub.a O.sub.b >20
M.sup.+ YO.sub.2 <0.05
Q/YO.sub.2 0.01-0.10
where Q comprises a N,N-diethyl-cis-2,6-dimethyl piperidinium cation; M is
an alkali metal cation; W is selected from the group aluminum, gallium,
iron, boron, titanium, indium, vanadium and mixtures thereof; a=1 or 2,
b=2 when a is 1 (i.e., W is tetravalent) and b=3 when a is 2 (i.e., W is
trivalent); and Y is selected from the group consisting of silicon,
germanium and mixtures thereof.
In accordance with this invention, there is also provided a zeolite
prepared by thermally treating a zeolite having a mole ratio of an oxide
selected from silicon oxide, germanium oxide and mixtures thereof to an
oxide selected from aluminum oxide, gallium oxide, iron oxide, boron
oxide, titanium oxide, indium oxide, vanadium oxide and mixtures thereof
greater than about 20 and having the X-ray diffraction lines of Table I at
a temperature of from about 200.degree. C. to about 800.degree. C., the
thus-prepared zeolite having the X-ray diffraction lines of Table II. The
present invention also includes this thus-prepared zeolite which is
predominantly in the hydrogen form, which hydrogen form is prepared by ion
exchanging with an acid or with a solution of an ammonium salt followed by
a second calcination. In accordance with the present invention there is
also provided a catalyst comprising the zeolite of this invention
predominantly in the hydrogen form.
Further provided in accordance with this invention is a catalyst comprising
the zeolite of this invention made substantially free of acidity by
neutralizing said zeolite with a basic metal.
The present invention further provides a catalyst comprising a zeolite of
this invention.
Also provided in accordance with the present invention is a method of
preparing a crystalline material comprising one or a combination of oxides
selected from the group consisting of oxides of one or more tetravalent
element(s) and one or more trivalent element(s), said method comprising
contacting under crystallization conditions sources of said oxides and a
templating agent comprising a N,N-diethyl-cis-2,6-dimethyl piperidinium
cation.
The present invention additionally provides a process for converting
hydrocarbons comprising contacting a hydrocarbonaceous feed at hydrocarbon
converting conditions with a catalyst comprising the zeolite of this
invention.
Further provided by the present invention is a hydrocracking process
comprising contacting a hydrocarbon feedstock under hydrocracking
conditions with a catalyst comprising the zeolite of this invention,
preferably predominantly in the hydrogen form.
This invention also includes a dewaxing process comprising contacting a
hydrocarbon feedstock under dewaxing conditions with a catalyst comprising
the zeolite of this invention, preferably predominantly in the hydrogen
form.
Also included in this invention is a process for increasing the octane of a
hydrocarbon feedstock to produce a product having an increased aromatics
content comprising contacting a hydrocarbonaceous feedstock which
comprises normal and slightly branched hydrocarbons having a boiling range
above about 40.degree. C. and less than about 200.degree. C., under
aromatic conversion conditions with a catalyst comprising the zeolite of
this invention made substantially free of acidity by neutralizing said
zeolite with a basic metal. Also provided in this invention is such a
process wherein the zeolite contains a Group VIII metal component.
Also provided by the present invention is a catalytic cracking process
comprising contacting a hydrocarbon feedstock in a reaction zone under
catalytic cracking conditions in the absence of added hydrogen with a
catalyst comprising the zeolite of this invention, preferably
predominantly in the hydrogen form. Also included in this invention is
such a catalytic cracking process wherein the catalyst additionally
comprises a large pore crystalline cracking component.
The present invention further provides an isomerizing process for
isomerizing C.sub.4 to C.sub.7 hydrocarbons, comprising contacting a
catalyst, comprising at least one Group VIII metal and the zeolite of this
invention, preferably predominantly in the hydrogen form, with a feed
having normal and slightly branched C.sub.4 to C.sub.7 hydrocarbons under
isomerizing conditions. Also provided is such an isomerization process
wherein the catalyst has been calcined in a steam/air mixture at an
elevated temperature after impregnation of the Group VIII metal,
preferably platinum.
This invention also provides a process for alkylating an aromatic
hydrocarbon which comprises contacting under alkylation conditions at
least a mole excess of an aromatic hydrocarbon with a C.sub.2 to C.sub.20
olefin under at least partial liquid phase conditions and in the presence
of a catalyst comprising the zeolite of this invention, preferably
predominantly in the hydrogen form.
This invention additionally provides a process for transalkylating an
aromatic hydrocarbon which comprises contacting under transalkylating
conditions an aromatic hydrocarbon with a polyalkyl aromatic hydrocarbon
under at least partial liquid phase conditions and in the presence of a
catalyst comprising the zeolite of this invention, preferably
predominantly in the hydrogen form.
Further provided by this invention is a process to convert paraffins to
aromatics which comprises contacting paraffins with a catalyst comprising
the zeolite of this invention, preferably predominantly in the hydrogen
form, said catalyst comprising gallium, zinc, or a compound of gallium or
zinc.
This invention also provides a process for converting lower alcohols and
other oxygenated hydrocarbons comprising contacting said lower alcohol or
other oxygenated hydrocarbon with a catalyst comprising the zeolite of
this invention, preferably predominantly in the hydrogen form, under
conditions to produce liquid products.
Further provided in accordance with this invention is a process for
isomerizing an isomerization feed comprising an aromatic C.sub.8 stream of
xylene isomers or mixtures of xylene isomers and ethylbenzene, wherein a
more nearly equilibrium ratio of ortho-, meta and para-xylenes is
obtained, said process comprising contacting said feed under isomerization
conditions with a catalyst comprising the zeolite of this invention,
preferably predominantly in the hydrogen form.
The present invention further provides a process for oligomerizing olefins
comprising contacting an olefin feed under oligomerization conditions with
a catalyst comprising the zeolite of this invention, preferably
predominantly in the hydrogen form.
Also provided by the present invention is an improved process for the
reduction of oxides of nitrogen contained in a gas stream in the presence
of oxygen wherein said process comprises contacting the gas stream with a
zeolite, the improvement comprising using as the zeolite a zeolite having
a mole ratio of an oxide of a first tetravalent element to an oxide of a
second tetravalent trivalent element different from said first tetravalent
element, said mole ratio being greater than about 20 and having the X-ray
diffraction lines of Table I. The zeolite may contain a metal or metal
ions capable of catalyzing the reduction of the oxides of nitrogen, and
may be conducted in the presence of a stoichiometric excess of oxygen. In
a preferred embodiment, the gas stream is the exhaust stream of an
internal combustion engine.
DETAILED DESCRIPTION OF THE INVENTION
The present invention comprises a family of crystalline, large pore
zeolites, SSZ-44. As used herein the term "large pore" means having an
average pore size diameter greater than about 6 Angstroms, preferably from
about 6.5 Angstroms to about 7.5 Angstroms.
In preparing SSZ-44 zeolites, a N,N-diethyl-cis-2,6-dimethyl piperidinium
cation is used as a crystallization template. In general, SSZ-44 is
prepared by contacting an active source of one or more oxides selected
from the group consisting of monovalent element oxides, divalent element
oxides, trivalent element oxides, and tetravalent element oxides with the
N,N-diethyl-cis-2,6-dimethyl piperidinium cation templating agent.
SSZ-44 is prepared from a reaction mixture having the composition shown in
Table A below.
TABLE A
______________________________________
Reaction Mixture
Typical Preferred
______________________________________
YO.sub.2 /W.sub.a O.sub.b
20 and greater
25 and greater
OH-/YO.sub.2
0.1 to 0.5 0.15 to 0.40
Q/YO.sub.2 0.05 to 0.40 0.10 to 0.30
M+/YO.sub.2 0.05 to 0.40 0.05 to 0.30
H.sub.2 O/YO.sub.2
15 to 100 20 to 50
______________________________________
where Q comprises a N,N-diethyl-cis-2,6-dimethyl piperidinium cation; M is
an alkali metal cation; W is selected from the group aluminum, gallium,
iron, boron, titanium, indium, vanadium and mixtures thereof; a=1 or 2,
b=2 when a is 1 (i.e., W is tetravalent) and b=3 when a is 2 (i.e., W is
trivalent); and Y is selected from the group consisting of silicon,
germanium and mixtures thereof. In practice, SSZ-44 is prepared by a
process comprising:
(a) preparing an aqueous solution containing sources of at least one oxide
capable of forming a crystalline molecular sieve and a
N,N-diethyl-cis-2,6-dimethyl piperidinium cation having an anionic
counterion which is not detrimental to the formation of SSZ-44;
(b) maintaining the aqueous solution under conditions sufficient to form
crystals of SSZ-44; and
(c) recovering the crystals of SSZ-44.
Accordingly, SSZ-44 may comprise the crystalline material and the
templating agent in combination with metallic and non-metallic oxides
bonded in tetrahedral coordination through shared oxygen atoms to form a
cross-linked three dimensional crystal structure. The metallic and
non-metallic oxides comprise one or a combination of oxides of a first
tetravalent element(s), and one or a combination of a second trivalent or
tetravalent element(s) different from the first tetravalent element(s).
The first tetravalent element(s) is preferably selected from the group
consisting of silicon, germanium and combinations thereof. More
preferably, the first tetravalent element is silicon. The second trivalent
or tetravalent element (which is different from the first tetravalent
element) is preferably selected from the group consisting of aluminum,
gallium, iron, boron, titanium, indium, vanadium and combinations thereof.
More preferably, the second trivalent or tetravalent element is aluminum,
boron or titanium.
Typical sources of aluminum oxide for the reaction mixture include
aluminates, alumina, aluminum colloids, aluminum oxide coated on silica
sol, hydrated alumina gels such as Al(OH).sub.3 and aluminum compounds
such as AlCl.sub.3 and Al.sub.2 (SO.sub.4).sub.3. Typical sources of
silicon oxide include silicates, silica hydrogel, silicic acid, fumed
silica, colloidal silica, tetra-alkyl orthosilicates, and silica
hydroxides. Boron, as well as gallium, germanium, titanium, indium,
vanadium and iron can be added in forms corresponding to their aluminum
and silicon counterparts.
A source zeolite reagent may provide a source of aluminum or boron. In most
cases, the source zeolite also provides a source of silica. The source
zeolite in its dealuminated or deboronated form may also be used as a
source of silica, with additional silicon added using, for example, the
conventional sources listed above. Use of a source zeolite reagent as a
source of alumina for the present process is more completely described in
U.S. Pat. No. 4,503,024 issued on Mar. 5, 1985 to Bourgogne, et al.
entitled
"PROCESS FOR THE PREPARATION OF SYNTHETIC ZEOLITES, AND ZEOLITES OBTAINED
BY SAID PROCESS", the disclosure of which is incorporated herein by
reference.
Typically, an alkali metal hydroxide and/or an alkaline earth metal
hydroxide, such as the hydroxide of sodium, potassium, lithium, cesium,
rubidium, calcium, and magnesium, is used in the reaction mixture;
however, this component can be omitted so long as the equivalent basicity
is maintained. The templating agent may be used to provide hydroxide ion.
Thus, it may be beneficial to ion exchange, for example, the halide for
hydroxide ion, thereby reducing or eliminating the alkali metal hydroxide
quantity required. The alkali metal cation or alkaline earth cation may be
part of the as-synthesized crystalline oxide material, in order to balance
valence electron charges therein. The reaction mixture is maintained at an
elevated temperature until the crystals of the SSZ-44 zeolite are formed.
The hydrothermal crystallization is usually conducted under autogenous
pressure, at a temperature between 100.degree. C. and 200.degree. C.,
preferably between 135.degree. and 180.degree. C. The crystallization
period is typically greater than 1 day and preferably from about 3 days to
about 20 days.
Preferably the zeolite is prepared using mild stirring or agitation.
During the hydrothermal crystallization step, the SSZ-44 crystals can be
allowed to nucleate spontaneously from the reaction mixture. The use of
SSZ-44 crystals as seed material can be advantageous in decreasing the
time necessary for complete crystallization to occur. In addition, seeding
can lead to an increased purity of the product obtained by promoting the
nucleation and/or formation of SSZ-44 over any undesired phases. When used
as seeds, SSZ-44 crystals are added in an amount between 0.1 and 10% of
the weight of silica used in the reaction mixture.
Once the zeolite crystals have formed, the solid product is separated from
the reaction mixture by standard mechanical separation techniques such as
filtration. The crystals are water-washed and then dried, e.g., at
90.degree. C. to 150.degree. C. for from 8 to 24 hours, to obtain the
as-synthesized SSZ-44 zeolite crystals. The drying step can be performed
at atmospheric pressure or under vacuum.
Accordingly, SSZ-44 comprises one or a combination of oxides, said oxides
being selected from monovalent elements, divalent elements, trivalent
elements, and tetravalent elements. The crystalline material as
synthesized will also contain a templating agent.
SSZ-44 as prepared has a mole ratio of an oxide selected from silicon
oxide, germanium oxide and mixtures thereof to an oxide selected from
aluminum oxide, gallium oxide, iron oxide, boron oxide, titanium oxide,
indium oxide, vanadium oxide and mixtures thereof greater than about 20;
and has the X-ray diffraction lines of Table I below. SSZ-44 further has a
composition, as synthesized and in the anhydrous state, in terms of mole
ratios, shown in Table B below.
TABLE B
______________________________________
As-Synthesized SSZ-44
______________________________________
YO.sub.2 /W.sub.a O.sub.b
>20 (preferably, 20 to about 400)
M.sup.+ /YO.sub.2
<0.05 (preferably, about 0.00005-0.05)
Q/YO.sub.2 0.01-0.10
______________________________________
where Q comprises a N,N-diethyl-cis-2,6-dimethyl piperidinium cation; M is
an alkali metal cation; W is selected from the group aluminum, gallium,
iron, boron, titanium, indium, vanadium and mixtures thereof; a=1 or 2,
b=2 when a is 1 (i.e., W is tetravalent) and b=3 when a is 2 (i.e., W is
trivalent); and Y is selected from the group consisting of silicon,
germanium and mixtures thereof.
SSZ-44 can be made essentially aluminum free, i.e., having a silica to
alumina mole ratio of .alpha.. The term "essentially alumina-free" is used
because it is difficult to prepare completely aluminum-free reaction
mixtures for synthesizing these materials. Especially when commercial
silica sources are used, aluminum is almost always present to a greater or
lesser degree. The hydrothermal reaction mixtures from which the
essentially alumina-free crystalline siliceous molecular sieves may be
prepared can be referred to as being substantially alumina-free. By this
usage is meant that no aluminum is intentionally added to the reaction
mixture, e.g., as an alumina or aluminate reagent, and that to the extent
aluminum is present, it occurs only as a contaminant in the reagents. An
additional method of increasing the mole ratio of silica to alumina is by
using standard acid leaching or chelating treatments. However, essentially
aluminum-free SSZ-44 can be synthesized directly using essentially
aluminum-free silicon sources as the only tetrahedral metal oxide
component. SSZ-44 can also be prepared directly as either an
aluminosilicate or a borosilicate.
Lower silica to alumina ratios may also be obtained by using methods which
insert aluminum into the crystalline framework. For example, aluminum
insertion may occur by thermal treatment of the zeolite in combination
with an alumina binder or dissolved source of alumina. Such procedures are
described in U.S. Pat. No. 4,559,315, issued on Dec. 17, 1985 to Chang, et
al.
It is believed that SSZ-44 is comprised of a new framework structure or
topology which is characterized by its X-ray diffraction pattern. SSZ-44
zeolites, as-synthesized, have a crystalline structure whose X-ray powder
diffraction pattern exhibit the characteristic lines shown in Table I and
is thereby distinguished from other known zeolites.
TABLE I
______________________________________
As-Synthesized SSZ-44
2 Theta d Relative Intensity.sup.(a)
______________________________________
7.7 11.4 M
8.0 11.0 VS
8.7 10.2 M
16.0 5.6 M
19.0 4.6 VS
19.6 4.5 M
20.5 4.3 M
21.6 4.1 M
23.7 3.8 M
25.5 3.5 S
______________________________________
.sup.(a) The Xray patterns provided are based on a relative intensity
scale in which the strongest line in the Xray pattern is assigned a value
of 100: W(weak) is less than 20; M(medium) is between 20 and 40; S(strong
is between 40 and 60; VS(very strong) is greater than 60.
After calcination, the SSZ-44 zeolites have a crystalline structure whose
X-ray powder diffraction pattern include the characteristic lines shown in
Table II:
TABLE II
______________________________________
Calcined SSZ-44
2 Theta d Relative Intensity
______________________________________
7.7 11.4 M-S
8.0 11.0 VS
8.7 10.2 S-VS
16.0 5.5 W
19.2 4.6 M
19.6 4.5 W
20.5 4.3 W
21.6 4.1 W
23.8 3.7 W
25.6 3.5 W
______________________________________
The X-ray powder diffraction patterns were determined by standard
techniques. The radiation was the K-alpha/doublet of copper. The peak
heights and the positions, as a function of 2.theta. where .theta. is the
Bragg angle, were read from the relative intensities of the peaks, and d,
the interplanar spacing in Angstroms corresponding to the recorded lines,
can be calculated.
The variation in the scattering angle (two theta) measurements, due to
instrument error and to differences between individual samples, is
estimated at +/-0.20 degrees.
The X-ray diffraction pattern of Table I is representative of
"as-synthesized" or "as-made" SSZ-44 zeolites. Minor variations in the
diffraction pattern can result from variations in the silica-to-alumina or
silica-to-boron mole ratio of the particular sample due to changes in
lattice constants. In addition, sufficiently small crystals will affect
the shape and intensity of peaks, leading to significant peak broadening.
Representative peaks from the X-ray diffraction pattern of calcined SSZ-44
are shown in Table II. Calcination can also result in changes in the
intensities of the peaks as compared to patterns of the "as-made"
material, as well as minor shifts in the diffraction pattern. The zeolite
produced by exchanging the metal or other cations present in the zeolite
with various other cations (such as H.sup.+ or NH.sub.4.sup.+) yields
essentially the same diffraction pattern, although again, there may be
minor shifts in the interplanar spacing and variations in the relative
intensities of the peaks. Notwithstanding these minor perturbations, the
basic crystal lattice remains unchanged by these treatments.
Crystalline SSZ-44 can be used as-synthesized, but preferably will be
thermally treated (calcined). Usually, it is desirable to remove the
alkali metal cation by ion exchange and replace it with hydrogen,
ammonium, or any desired metal ion. The zeolite can be leached with
chelating agents, e.g., EDTA or dilute acid solutions, to increase the
silica to alumina mole ratio. The zeolite can also be steamed; steaming
helps stabilize the crystalline lattice to attack from acids.
The zeolite can be used in intimate combination with hydrogenating
components, such as tungsten, vanadium molybdenum, rhenium, nickel cobalt,
chromium, manganese, or a noble metal, such as palladium or platinum, for
those applications in which a hydrogenation-dehydrogenation function is
desired.
Metals may also be introduced into the zeolite by replacing some of the
cations in the zeolite with metal cations via ion exchange techniques.
Typical replacing cations can include metal cations, e.g., rare earth,
Group IIA and Group VIII metals, as well as their mixtures. Of the
replacing metallic cations, cations of metals such as rare earth, Mn, Ca,
Mg, Zn, Cd, Pt, Pd, Ni, Co, Ti, Al, Sn, and Fe are particularly preferred.
The hydrogen, ammonium, and metal components can be ion-exchanged into the
SSZ-44. The zeolite can also be impregnated with the metals, or, the
metals can be physically and intimately admixed with the zeolite using
standard methods known to the art.
Typical ion-exchange techniques involve contacting the synthetic zeolite
with a solution containing a salt of the desired replacing cation or
cations. Although a wide variety of salts can be employed, chlorides and
other halides, acetates, nitrates, and sulfates are particularly
preferred. The zeolite is usually calcined prior to the ion-exchange
procedure to remove the organic matter present in the channels and on the
surface, since this results in a more effective ion exchange.
Representative ion exchange techniques are disclosed in a wide variety of
patents including U.S. Pat. No. 3,140,249 issued on Jul. 7, 1964 to Plank,
et al.; U.S. Pat. No. 3,140,251 issued on Jul. 7, 1964 to Plank, et al.;
and U.S. Pat. No. 3,140,253 issued on Jul. 7, 1964 to Plank, et al.
Following contact with the salt solution of the desired replacing cation,
the zeolite is typically washed with water and dried at temperatures
ranging from 65.degree. C. to about 200.degree. C. After washing, the
zeolite can be calcined in air or inert gas at temperatures ranging from
about 200.degree. C. to about 800.degree. C. for periods of time ranging
from 1 to 48 hours, or more, to produce a catalytically active product
especially useful in hydrocarbon conversion processes.
Regardless of the cations present in the synthesized form of SSZ-44, the
spatial arrangement of the atoms which form the basic crystal lattice of
the zeolite remains essentially unchanged. The exchange of cations has
little, if any effect on the zeolite lattice structure.
SSZ-44 can be formed into a wide variety of physical shapes. Generally
speaking, the zeolite can be in the form of a powder, a granule, or a
molded product, such as extrudate having a particle size sufficient to
pass through a 2-mesh (Tyler) screen and be retained on a 400-mesh (Tyler)
screen. In cases where the catalyst is molded, such as by extrusion with
an organic binder, the aluminosilicate can be extruded before drying, or,
dried or partially dried and then extruded.
SSZ-44 can be composited with other materials resistant to the temperatures
and other conditions employed in organic conversion processes. Such matrix
materials include active and inactive materials and synthetic or naturally
occurring zeolites as well as inorganic materials such as clays, silica
and metal oxides. Examples of such materials and the manner in which they
can be used are disclosed in U.S. Pat. No. 4,910,006, issued May 20, 1990
to Zones et al., and U.S. Pat. No. 5,316,753, issued May 31, 1994 to
Nakagawa, both of which are incorporated by reference herein in their
entirety.
Hydrocarbon Conversion Processes
SSZ-44 zeolites are useful in hydrocarbon conversion reactions. Hydrocarbon
conversion reactions are chemical and catalytic processes in which carbon
containing compounds are changed to different carbon containing compounds.
Examples of hydrocarbon conversion reactions in which SSZ-44 are expected
to be useful include catalytic cracking, hydrocracking, dewaxing,
alkylation, and olefin and aromatics formation reactions. The catalysts
are also expected to be useful in other petroleum refining and hydrocarbon
conversion reactions such as isomerizing n-paraffins and naphthenes,
polymerizing and oligomerizing olefinic or acetylenic compounds such as
isobutylene and butene-1, reforming, alkylating, isomerizing polyalkyl
substituted aromatics (e.g., m-xylene), and disproportionating aromatics
(e.g., toluene) to provide mixtures of benzene, xylenes and higher
methylbenzenes and oxidation reactions. The SSZ-44 catalysts have high
selectivity, and under hydrocarbon conversion conditions can provide a
high percentage of desired products relative to total products.
SSZ-44 zeolites can be used in processing hydrocarbonaceous feedstocks.
Hydrocarbonaceous feedstocks contain carbon compounds and can be from many
different sources, such as virgin petroleum fractions, recycle petroleum
fractions, shale oil, liquefied coal, tar sand oil, and, in general, can
be any carbon containing fluid susceptible to zeolitic catalytic
reactions. Depending on the type of processing the hydrocarbonaceous feed
is to undergo, the feed can contain metal or be free of metals, it can
also have high or low nitrogen or sulfur impurities. It can be
appreciated, however, that in general processing will be more efficient
(and the catalyst more active) the lower the metal, nitrogen, and sulfur
content of the feedstock.
The conversion of hydrocarbonaceous feeds can take place in any convenient
mode, for example, in fluidized bed, moving bed, or fixed bed reactors
depending on the types of process desired. The formulation of the catalyst
particles will vary depending on the conversion process and method of
operation.
Other reactions which can be performed using the catalyst of this invention
containing a metal, e.g., a Group VIII metal such platinum, include
hydrogenation-dehydrogenation reactions, denitrogenation and
desulfurization reactions.
SSZ-44 can be used in hydrocarbon conversion reactions with active or
inactive supports, with organic or inorganic binders, and with and without
added metals. These reactions are well known to the art, as are the
reaction conditions.
Hydrocracking
Using a catalyst which comprises SSZ-44 in the hydrogen form and a
hydrogenation promoter, heavy petroleum residual feedstocks, cyclic stocks
and other hydrocrackate charge stocks can be hydrocracked using the
process conditions and catalyst components disclosed in the aforementioned
U.S. Pat. No. 4,910,006 and U.S. Pat. No. 5,316,753. Typically, these
feedstocks can be hydrocracked at hydrocracking conditions including a
temperature in the range of from 175.degree. C. to 485.degree. C., molar
ratios of hydrogen to hydrocarbon charge from 1 to 100, a pressure in the
range of from 0.5 to 350 bar, and a liquid hourly space velocity (LHSV) in
the range of from 0.1 to 30.
The hydrocracking catalysts contain an effective amount of at least one
hydrogenation component of the type commonly employed in hydrocracking
catalysts. The hydrogenation component is generally selected from the
group of hydrogenation catalysts consisting of one or more metals of Group
VIB and Group VIII, including the salts, complexes and solutions
containing such. The hydrogenation catalyst is preferably selected from
the group of metals, salts and complexes thereof of the group consisting
of at least one of platinum, palladium, rhodium, iridium and mixtures
thereof or the group consisting of at least one of nickel, molybdenum,
cobalt, tungsten, titanium, chromium and mixtures thereof. Reference to
the catalytically active metal or metals is intended to encompass such
metal or metals in the elemental state or in some form such as an oxide,
sulfide, halide, carboxylate and the like.
The hydrogenation catalyst is present in an effective amount to provide the
hydrogenation function of the hydrocracking catalyst, and preferably in
the range of from 0.05 to 25% by weight.
Dewaxing
SSZ-44 in the hydrogen form can be used to dewax hydrocarbonaceous feeds by
selectively removing straight chain paraffins. Typically, the viscosity
index of the dewaxed product is improved (compared to the waxy feed) when
the waxy feed is contacted with SSZ-44 under isomerization dewaxing
conditions.
The catalytic dewaxing conditions are dependent in large measure on the
feed used and upon the desired pour point. Generally, the temperature will
be between about 200.degree. C. and about 475.degree. C., preferably
between about 250.degree. C. and about 450.degree. C. The pressure is
typically between about 15 psig and about 3000 psig, preferably between
about 200 psig and 3000 psig. The liquid hourly space velocity (LHSV)
preferably will be from 0.1 to 20, preferably between about 0.2 and about
10.
Hydrogen is preferably present in the reaction zone during the catalytic
dewaxing process. The hydrogen to feed ratio is typically between about
500 and about 30,000 SCF/bbl (standard cubic feet per barrel), preferably
about 1000 to about 20,000 SCF/bbl. Generally, hydrogen will be separated
from the product and recycled to the reaction zone. Typical feedstocks
include light gas oil, heavy gas oils and reduced crudes boiling about
350.degree. F.
A typical dewaxing process is the catalytic dewaxing of a hydrocarbon oil
feedstock boiling above about 350.degree. F. and containing straight chain
and slightly branched chain hydrocarbons by contacting the hydrocarbon oil
feedstock in the presence of added hydrogen gas at a hydrogen pressure of
about 15-3000 psi with a catalyst comprising SSZ-44 and at least one group
VIII metal.
The SSZ-44 hydrodewaxing catalyst may optionally contain a hydrogenation
component of the type commonly employed in dewaxing catalysts. See the
aforementioned U.S. Pat. No. 4,910,006 and U.S. Pat. No. 5,316,753 for
examples of these hydrogenation components.
The hydrogenation component is present in an effective amount to provide an
effective hydrodewaxing and hydroisomerization catalyst preferably in the
range of from about 0.05 to 5% by weight. The catalyst may be run in such
a mode to increase isodewaxing at the expense of cracking reactions.
The feed may be hydrocracked, followed by dewaxing. This type of two stage
process and typical hydrocracking conditions are described in U.S. Pat.
No. 4,921,594, issued May 1, 1990 to Miller, which is incorporated herein
by reference in its entirety.
The zeolite of this invention may also be utilized as a dewaxing catalyst
in the form of a layered catalyst. That is, the catalyst comprises a first
layer comprising zeolite SSZ-44 and at least one Group VIII metal, and a
second layer comprising an aluminosilicate zeolite which is more shape
selective than zeolite SSZ-44. The use of layered catalysts is disclosed
in U.S. Pat. No. 5,149,421, issued Sep. 22, 1992 to Miller, which is
incorporated by reference herein in its entirety.
The zeolite of this invention may also be used to dewax raffinates,
including bright stock, under conditions such as those disclosed in U.S.
Pat. No. 4,181,598, issued Jan. 1, 1980 to Gillespie et al., which is
incorporated by reference herein in its entirety.
It is often desirable to use mild hydrogenation (sometimes referred to as
hydrofinishing) to produce more stable dewaxed products. The
hydrofinishing step can be performed either before or after the dewaxing
step, and preferably after. Hydrofinishing is typically conducted at
temperatures ranging from about 190.degree. C. to about 340.degree. C. at
pressures from about 400 psig to about 3000 psig at space velocities
(LHSV) between about 0.1 and 20 and a hydrogen recycle rate of about 400
to 1500 SCF/bbl. The hydrogenation catalyst employed must be active enough
not only to hydrogenate the olefins, diolefins and color bodies which may
be present, but also to reduce the aromatic content. Suitable
hydrogenation catalyst are disclosed in U.S. Pat. No. 4,921,594, issued
May 1, 1990 to Miller, which is incorporated by reference herein in its
entirety. The hydrofinishing step is beneficial in preparing an acceptably
stable product (e.g., a lubricating oil) since dewaxed products prepared
from hydrocracked stocks tend to be unstable to air and light and tend to
form sludges spontaneously and quickly.
Lube oil may be prepared using SSZ-44. For example, a C.sub.20+ lube oil
may be made by isomerizing a C.sub.20+ olefin feed over a catalyst
comprising SSZ-44 in the hydrogen form and at least one Group VIII metal.
Alternatively, the lubricating oil may be made by hydrocracking in a
hydrocracking zone a hydrocarbonaceous feedstock to obtain an effluent
comprising a hydrocracked oil, and catalytically dewaxing the effluent at
a temperature of at least about 400.degree. F. and at a pressure of from
about 15 psig to about 3000 psig in the presence of added hydrogen gas
with a catalyst comprising SSZ-44 in the hydrogen form and at least one
Group VIII metal.
Aromatics Formation
SSZ-44 can be used to convert light straight run naphthas and similar
mixtures to highly aromatic mixtures. Thus, normal and slightly branched
chained hydrocarbons, preferably having a boiling range above about
40.degree. C. and less than about 200.degree. C., can be converted to
products having a substantial higher octane aromatics content by
contacting the hydrocarbon feed with the zeolite at a temperature in the
range of from about 400.degree. C. to 600.degree. C., preferably
480.degree. C. to 550.degree. C. at pressures ranging from atmospheric to
10 bar, and liquid hourly space velocities (LHSV) ranging from 0.1 to 15.
The conversion catalyst preferably contains a Group VIII metal compound to
have sufficient activity for commercial use. By Group VIII metal compound
as used herein is meant the metal itself or a compound thereof. The Group
VIII noble metals and their compounds, platinum, palladium, and iridium,
or combinations thereof can be used. Rhenium or tin or a mixture thereof
may also be used in conjunction with the Group VIII metal compound and
preferably a noble metal compound. The most preferred metal is platinum.
The amount of Group VIII metal present in the conversion catalyst should
be within the normal range of use in reforming catalysts, from about 0.05
to 2.0 weight percent, preferably 0.2 to 0.8 weight percent.
It is critical to the selective production of aromatics in useful
quantities that the conversion catalyst be substantially free of acidity,
for example, by neutralizing the zeolite with a basic metal, e.g., alkali
metal, compound. Methods for rendering the catalyst free of acidity are
known in the art. See the aforementioned U.S. Pat. No. 4,910,006 and U.S.
Pat. No. 5,316,753 for a description of such methods.
The preferred alkali metals are sodium, potassium, and cesium. The zeolite
itself can be substantially free of acidity only at very high
silica:alumina mole ratios; by "zeolite consisting essentially of silica"
is meant a zeolite which is substantially free of acidity without base
neutralization.
Catalytic Cracking
Hydrocarbon cracking stocks can be catalytically cracked in the absence of
hydrogen using SSZ-44 in the hydrogen form at liquid hourly space
velocities from 0.5 to 50, temperatures from about 260.degree. F. to
1625.degree. F. and pressures from subatmospheric to several hundred
atmospheres, typically from about atmospheric to about 5 atmospheres.
For this purpose, the SSZ-44 catalyst can be composited with mixtures of
inorganic oxide supports as well as traditional cracking catalyst.
As in the case of hydrocracking catalysts, when SSZ-44 is used as a
catalytic cracking catalyst in the absence of hydrogen, the catalyst may
be employed in conjunction with traditional cracking catalysts, e.g., any
aluminosilicate heretofore employed as a component in cracking catalysts.
Typically, these are large pore, crystalline aluminosilicates. Examples of
these traditional cracking catalysts are disclosed in the aforementioned
U.S. Pat. No. 4,910,006 and U.S. Pat. No. 5,316,753. When a traditional
cracking catalyst (TC) component is employed, the relative weight ratio of
the TC to the SSZ-44 is generally between about 1:10 and about 500:1,
desirably between about 1:10 and about 200:1, preferably between about 1:2
and about 50:1, and most preferably is between about 1:1 and about 20:1.
The cracking catalysts are typically employed with an inorganic oxide
matrix component. See the aforementioned U.S. Pat. No. 4,910,006 and U.S.
Pat. No. 5,316,753 for examples of such matrix components.
Oligomerization
It is expected that SSZ-44 in the hydrogen form can also be used to
oligomerize straight and branched chain olefins having from about 2 to 21
and preferably 2-5 carbon atoms. The oligomers which are the products of
the process are medium to heavy olefins which are useful for both fuels,
i.e., gasoline or a gasoline blending stock and chemicals.
The oligomerization process comprises contacting the olefin feedstock in
the gaseous state phase with SSZ-44 at a temperature of from about
450.degree. F. to about 1200.degree. F., a LHSV of from about 0.2 to about
50 and a hydrocarbon partial pressure of from about 0.1 to about 50
atmospheres.
Also, temperatures below about 450.degree. F. may be used to oligomerize
the feedstock, when the feedstock is in the liquid phase when contacting
the zeolite catalyst. Thus, when the olefin feedstock contacts the zeolite
catalyst in the liquid phase, temperatures of from about 50.degree. F. to
about 450.degree. F., and preferably from 80.degree. F. to 400.degree. F.
may be used and a WHSV of from about 0.05 to 20 and preferably 0.1 to 10.
It will be appreciated that the pressures employed must be sufficient to
maintain the system in the liquid phase. As is known in the art, the
pressure will be a function of the number of carbon atoms of the feed
olefin and the temperature. Suitable pressures include from about 0 psig
to about 3000 psig.
The zeolite can have the original cations associated therewith replaced by
a wide variety of other cations according to techniques well known in the
art. Typical cations would include hydrogen, ammonium and metal cations
including mixtures of the same. Of the replacing metallic cations,
particular preference is given to cations of metals such as rare earth
metals, manganese, calcium, as well as metals of Group II of the Periodic
Table, e.g., zinc, and Group VIII of the Periodic Table, e.g., nickel. One
of the prime requisites is that the zeolite have a fairly low
aromatization activity, i.e., in which the amount of aromatics produced is
not more than about 20% by weight. This is accomplished by using a zeolite
with controlled acid activity [alpha value] of from about 0.1 to about
120, preferably from about 0.1 to about 100, as measured by its ability to
crack n-hexane.
Alpha values are defined by a standard test known in the art, e.g., as
shown in U.S. Pat. No. 3,960,978 issued on Jun. 1, 1976 to Givens, et al.
which is incorporated totally herein by reference. If required, such
zeolites may be obtained by steaming, by use in a conversion process or by
any other method which may occur to one skilled in this art.
SSZ-44 can be used to convert light gas C.sub.2 -C.sub.6 paraffins and/or
olefins to higher molecular weight hydrocarbons including aromatic
compounds. Operating temperatures of 100.degree. C. to 700.degree. C.,
operating pressures of 0 to 1000 psig and space velocities of 0.5-40
hr.sup.-1 WHSV (weight hourly space velocity) can be used to convert the
C.sub.2 -C.sub.6 paraffin and/or olefins to aromatic compounds.
Preferably, the zeolite will contain a catalyst metal or metal oxide
wherein said metal is selected from the group consisting of Groups IB,
IIB, VIII and IIIA of the Periodic Table, and most preferably gallium or
zinc and in the range of from about 0.05 to 5% by weight.
Conversion of Paraffins to Aromatics
SSZ-44 in the hydrogen form can be used to convert light gas C.sub.2
-C.sub.6 paraffins to higher molecular weight hydrocarbons including
aromatic compounds. Operating temperatures of 100.degree.-700.degree. C.,
operating pressures of 0 to 1000 psig and space velocities of 0.5-40
hr.sup.-1 WHSV can be used to convert the paraffin to aromatic compounds.
Preferably, the zeolite will contain a catalyst metal or metal oxide
wherein said metal is selected from the group consisting of Group IB, IIB,
VIII and IIIA of the Periodic Table. Preferably the metal is gallium or
zinc in the range of from about 0.05 to 5% by weight.
Condensation of Alcohols
SSZ-44 can be used to condense lower aliphatic alcohols having 1 to 10
carbon atoms to a gasoline boiling point hydrocarbon product comprising
mixed aliphatic and aromatic hydrocarbon. The condensation reaction
proceeds at a temperature of about 500.degree. F. to 1000.degree. F., a
pressure of about 0.5 psig to 1000 psig and a space velocity of about 0.5
to 50 WHSV. The process disclosed in U.S. Pat. No. 3,894,107 issued Jul.
8, 1975 to Butter et al., describes the process conditions used in this
process, which patent is incorporated totally herein by reference.
The catalyst may be in the hydrogen form or may be base exchanged or
impregnated to contain ammonium or a metal cation complement, preferably
in the range of from about 0.05 to 5% by weight. The metal cations that
may be present include any of the metals of the Groups I through VIII of
the Periodic Table. However, in the case of Group IA metals, the cation
content should in no case be so large as to effectively inactivate the
catalyst.
Isomerization
The present catalyst is highly active and highly selective for isomerizing
C.sub.4 to C.sub.7 hydrocarbons. The activity means that the catalyst can
operate at relatively low temperature which thermodynamically favors
highly branched paraffins. Consequently, the catalyst can produce a high
octane product. The high selectivity means that a relatively high liquid
yield can be achieved when the catalyst is run at a high octane.
The present process comprises contacting the isomerization catalyst, i.e.,
a catalyst comprising SSZ-44 in the hydrogen form, with a hydrocarbon feed
under isomerization conditions. The feed is preferably a light straight
run fraction, boiling within the range of 30.degree. F. to 250.degree. F.
and preferably from 60.degree. F. to 200.degree. F. Preferably, the
hydrocarbon feed for the process comprises a substantial amount of C.sub.4
to C.sub.7 normal and slightly branched low octane hydrocarbons, more
preferably C.sub.5 and C.sub.6 hydrocarbons.
The pressure in the process is preferably between 50 psig and 1000 psig,
more preferably between 100 psig and 500 psig. The liquid hourly space
velocity (LHSV) is preferably between about 1 to about 10 with a value in
the range of about 1 to about 4 being more preferred. It is also
preferable to carry out the isomerization reaction in the presence of
hydrogen. Preferably, hydrogen is added to give a hydrogen to hydrocarbon
ratio (H.sub.2 /HC) of between 0.5 and 10 H.sub.2 /HC, more preferably
between 1 and 8 H.sub.2 /HC. The temperature is preferably between about
200.degree. F. and about 1000.degree. F., more preferably between
400.degree. F. and 600.degree. F. See the aforementioned U.S. Pat. No.
4,910,006 and U.S. Pat. No. 5,316,753 for a further discussion of
isomerization process conditions.
A low sulfur feed is especially preferred in the present process. The feed
preferably contains less than 10 ppm, more preferably less than 1 ppm, and
most preferably less than 0.1 ppm sulfur. In the case of a feed which is
not already low in sulfur, acceptable levels can be reached by
hydrogenating the feed in a presaturation zone with a hydrogenating
catalyst which is resistant to sulfur poisoning. See the aforementioned
U.S. Pat. No. 4,910,006 and U.S. Pat. No. 5,316,753 for a further
discussion of this hydrodesulfurization process.
It is preferable to limit the nitrogen level and the water content of the
feed. Catalysts and processes which are suitable for these purposes are
known to those skilled in the art.
After a period of operation, the catalyst can become deactivated by sulfur
or coke. See the aforementioned U.S. Pat. No. 4,910,006 and U.S. Pat. No.
5,316,753 for a further discussion of methods of removing this sulfur and
coke, and of regenerating the catalyst.
The conversion catalyst preferably contains a Group VIII metal compound to
have sufficient activity for commercial use. By Group VIII metal compound
as used herein is meant the metal itself or a compound thereof. The Group
VIII noble metals and their compounds, platinum, palladium, and iridium,
or combinations thereof can be used. Rhenium and tin may also be used in
conjunction with the noble metal. The most preferred metal is platinum.
The amount of Group VIII metal present in the conversion catalyst should
be within the normal range of use in isomerizing catalysts, from about
0.05 to 2.0 weight percent, preferably 0.2 to 0.8 weight percent.
Alkylation and Transalkylation
SSZ-44 can be used in a process for the alkylation or transalkylation of an
aromatic hydrocarbon. The process comprises contacting the aromatic
hydrocarbon with a C.sub.2 to C.sub.16 olefin alkylating agent or a
polyalkyl aromatic hydrocarbon transalkylating agent, under at least
partial liquid phase conditions, and in the presence of a catalyst
comprising SSZ-44.
SSZ-44 can also be used for removing benzene from gasoline by alkylating
the benzene as described above and removing the alkylated product from the
gasoline.
For high catalytic activity, the SSZ-44 zeolite should be predominantly in
its hydrogen ion form. Generally, the zeolite is converted to its hydrogen
form by ammonium exchange followed by calcination. If the zeolite is
synthesized with a high enough ratio of organo-nitrogen cation to sodium
ion, calcination alone may be sufficient. It is preferred that, after
calcination, at least 80% of the cation sites are occupied by hydrogen
ions and/or rare earth ions.
The pure SSZ-44 zeolite may be used as a catalyst, but generally it is
preferred to mix the zeolite powder with an inorganic oxide binder such as
alumina, silica, silica/alumina, or naturally occurring clays and form the
mixture into tablets or extrudates. The final catalyst may contain from 1
to 99 weight percent SSZ-44 zeolite. Usually the zeolite content will
range from 10 to 90 weight percent, and more typically from 60 to 80
weight percent. The preferred inorganic binder is alumina. The mixture may
be formed into tablets or extrudates having the desired shape by methods
well known in the art.
Examples of suitable aromatic hydrocarbon feedstocks which may be alkylated
or transalkylated by the process of the invention include aromatic
compounds such as benzene, toluene and xylene. The preferred aromatic
hydrocarbon is benzene. Mixtures of aromatic hydrocarbons may also be
employed.
Suitable olefins for the alkylation of the aromatic hydrocarbon are those
containing 2 to 20, preferably 2 to 4, carbon atoms, such as ethylene,
propylene, butene-1, trans-butene-2 and cis-butene-2, or mixtures thereof.
The preferred olefin is propylene. These olefins may be present in
admixture with the corresponding C.sub.2 to C.sub.20 paraffins, but it is
preferable to remove any dienes, acetylenes, sulfur compounds or nitrogen
compounds which may be present in the olefin feedstock stream, to prevent
rapid catalyst deactivation. Longer chain alpha olefins may be used as
well.
When transalkylation is desired, the transalkylating agent is a polyalkyl
aromatic hydrocarbon containing two or more alkyl groups that each may
have from 2 to about 4 carbon atoms. For example, suitable polyalkyl
aromatic hydrocarbons include di-, tri- and tetra-alkyl aromatic
hydrocarbons, such as diethylbenzene, triethylbenzene,
diethylmethylbenzene (diethyltoluene), di-isopropylbenzene,
di-isopropyltoluene, dibutylbenzene, and the like. Preferred polyalkyl
aromatic hydrocarbons are the dialkyl benzenes. A particularly preferred
polyalkyl aromatic hydrocarbon is di-isopropylbenzene.
When alkylation is the process conducted, reaction conditions are as
follows. The aromatic hydrocarbon feed should be present in stoichiometric
excess. It is preferred that molar ratio of aromatics to olefins be
greater than four-to-one to prevent rapid catalyst fouling. The reaction
temperature may range from 100.degree. F. to 600.degree. F., preferably
250.degree. F. to 450.degree. F. The reaction pressure should be
sufficient to maintain at least a partial liquid phase in order to retard
catalyst fouling. This is typically 50 psig to 1000 psig depending on the
feedstock and reaction temperature. Contact time may range from 10 seconds
to 10 hours, but is usually from 5 minutes to an hour. The weight hourly
space velocity (WHSV), in terms of grams (pounds) of aromatic hydrocarbon
and olefin per gram (pound) of catalyst per hour, is generally within the
range of about 0.5 to 50.
When transalkylation is the process conducted, the molar ratio of aromatic
hydrocarbon will generally range from about 1:1 to 25:1, and preferably
from about 2:1 to 20:1. The reaction temperature may range from about
100.degree. F. to 600.degree. F., but it is preferably about 250.degree.
F. to 450.degree. F. The reaction pressure should be sufficient to
maintain at least a partial liquid phase, typically in the range of about
50 psig to 1000 psig, preferably 300 psig to 600 psig. The weight hourly
space velocity will range from about 0.1 to 10. U.S. Pat. No. 5,082,990
issued on Jan. 21, 1992 to Hsieh, et al. describes such processes and is
incorporated herein by reference.
Xylene Isomerization
SSZ-44 in the hydrogen form may also be useful in a process for isomerizing
one or more xylene isomers in a C.sub.8 aromatic feed to obtain ortho-,
meta-, and para-xylene in a ratio approaching the equilibrium value. In
particular, xylene isomerization is used in conjunction with a separate
process to manufacture para-xylene. For example, a portion of the
para-xylene in a mixed C.sub.8 aromatics stream may be recovered by
crystallization and centrifugation. The mother liquor from the
crystallizer is then reacted under xylene isomerization conditions to
restore ortho-, meta- and paraxylenes to a near equilibrium ratio. At the
same time, part of the ethylbenzene in the mother liquor is converted to
xylenes or to products which are easily separated by filtration. The
isomerate is blended with fresh feed and the combined stream is distilled
to remove heavy and light by-products. The resultant C.sub.8 aromatics
stream is then sent to the crystallizer to repeat the cycle.
In the vapor phase, suitable isomerization conditions include a temperature
in the range of about 500.degree.-1100.degree. F., preferably about
600.degree.-1050.degree. F., a pressure in the range of about 0.5-50 atm
abs, preferably 1-5 atm abs, and a weight hourly space velocity (WHSV) of
0.1 to 100, preferably 0.5 to 50. Optionally, isomerization in the vapor
phase is conducted in the presence of 3.0 to 30.0 moles of hydrogen per
mole of alkylbenzene (e.g., ethylbenzene). If hydrogen is used, the
catalyst should comprise about 0.1 to 2.0 wt % of a
hydrogenation/dehydrogenation component selected from Group VIII (of the
Periodic Table) metal component, especially platinum or nickel. By Group
VIII metal component is meant the metals and their compounds such as
oxides and sulfides.
In the liquid phase, suitable isomerization conditions include a
temperature in the range of about 100.degree.-700.degree. F., a pressure
in the range of about 1-200 atm abs, and a WHSV in the range of about
0.5-50.
Optionally, the isomerization feed may contain 10 to 90 wt % of a diluent
such as toluene, trimethylbenzene, naphthenes or paraffins.
Other Uses for SSZ-44
SSZ-44 can also be used as an adsorbent with high selectivities based on
molecular sieve behavior and also based upon preferential hydrocarbon
packing within the pores.
SSZ-44 may also be used for the catalytic reduction of the oxides of
nitrogen in a gas stream. Typically the gas stream also contains oxygen,
often a stoichiometric excess thereof. Also, the SSZ-44 may contain a
metal or metal ions within or on it which are capable of catalyzing the
reduction of the nitrogen oxides. Examples of such metals or metal ions
include copper, cobalt and mixtures thereof.
One example of such a process for the catalytic reduction of oxides of
nitrogen in the presence of a zeolite is disclosed in U.S. Pat. No.
4,297,328, issued Oct. 27, 1981 to Ritscher et al., which is incorporated
by reference herein. There, the catalytic process is the combustion of
carbon monoxide and hydrocarbons and the catalytic reduction of the oxides
of nitrogen contained in a gas stream, such as the exhaust gas from an
internal combustion engine. The zeolite used is metal ion-exchanged, doped
or loaded sufficiently so as to provide an effective amount of catalytic
copper metal or copper ions within or on the zeolite. In addition, the
process is conducted in an excess of oxidant, e.g., oxygen.
EXAMPLES
The following examples demonstrate but do not limit the present invention.
Example 1
Synthesis of N,N-diethyl-cis-2,6-dimethylpiperidinium hydroxide (Template
A)
Thirty-six grams of cis-2,6-dimethylpiperidine was mixed with 320 ml of
methanol and 64 grams of potassium bicarbonate. Ethyl iodide (199 grams)
was added dropwise to the reaction mixture and, following complete
addition, the reaction was heated at reflux for three days. Following
isolation of the desired product, the salt was recrystallized from hot
acetone and ether with a small amount of methanol and the iodide salt was
converted to the hydroxide salt by treatment with Bio-Rad AG1-X8 anion
exchange resin. The hydroxide ion concentration was determined by
titration of the resulting solution using phenolphthalein as the
indicator.
Example 2
Preparation of Aluminosilicate SSZ-44 Starting SiO.sub.2 /Al.sub.2 O.sub.3
=100
Four grams of a solution of Template A (0.56 mmol OH.sup.- /g) was mixed
with 6.4 grams of water and 1.5 grams of 1.0N NaOH. Reheis F2000 hydrated
aluminum hydroxide (0.029 gram) was added to this solution and, following
complete dissolution of the solid, 0.92 gram of Cabosil M-5 fumed silica
was added. The resulting reaction mixture was sealed in a Parr 4745
reactor and heated at 170.degree. C. and rotated at 43 rpm. After seven
days, a settled product was obtained and determined by XRD to be SSZ-44.
Analysis of this product showed the SiO.sub.2 /Al.sub.2 O.sub.3 mole ratio
to be 80. Representative X-ray diffraction data for the product appears in
Table III below. In table III and subsequent tables, the intensity of each
peak is expressed as 100.times.I/I.sub.o, where I.sub.o is the intensity
of the strongest line or peak.
TABLE III
______________________________________
2 Theta d 100 .times. I/I.sub.o
______________________________________
7.70 11.48 23.3
8.01 11.03 82.7
8.68 10.18 32.3
12.59 7.03 7.6
15.31 5.78 17.5
15.92 5.56 24.8
16.98 5.22 5.4
17.84 4.97 10.2
19.11 4.64 100.0
19.64 4.52 30.0
20.06 4.42 4.2
20.45 4.34 26.3
20.18 4.19 7.4
21.59 4.11 18.0
21.91 4.05 8.6
22.38 3.97 5.5
23.30 3.82 11.0
23.48 3.79 6.5
23.71 3.75 28.8
24.38 3.65 18.2
24.66 3.61 28.8
24.82 3.58 27.0
25.06 3.55 32.6
25.50 3.49 46.5
26.22 3.40 15.2
26.98 3.30 22.2
27.60 3.23 10.5
28.42 3.14 9.7
28.80 3.10 6.2
29.56 3.02 5.6
29.81 2.99 4.6
30.93 2.89 5.5
______________________________________
Example 3
Preparation of Aluminosilicate SSZ-44 Starting SiO.sub.2 /Al.sub.2 Q.sub.3
=100
Four grams of a solution of Template A (0.56 mmol OH.sup.- /g) was mixed
with 4.3 grams of water and 1.5 grams of 1.0N NaOH. Reheis F2000 (0.029
gram) was added to this solution and, following complete dissolution of
the solid, 3.0 grams of Ludox AS-30 (DuPont) aqueous colloidal silica was
added. This mixture was heated at 170.degree. C. and rotated at 43 rpm for
12 days, after which a settled product was obtained. Analysis by XRD
showed the product to be SSZ-44.
Example 4
Seeded Preparation of Aluminosilicate SSZ-44
The reaction described in Example 2 was repeated, with the exception of
seeding with 0.006 gram of SSZ-44 crystals. In this case, SSZ-44 was
obtained in five days.
Example 5
Preparation of Aluminosilicate SSZ-44 Starting SiO.sub.2 /Al.sub.2 O.sub.3
=67
The reaction as described in Example 4 was repeated, with the exception of
using 0.044 gram of Reheis F2000 silica in the reaction mixture. This
resulted in a SiO.sub.2 /Al.sub.2 O.sub.3 mole ratio in the reaction
mixture of 67. After six days at 170.degree. C. (43 rpm) a product was
isolated and determined by X-ray diffraction data to be SSZ-44. X-ray
diffraction data for this product appears in Table IV below.
TABLE IV
______________________________________
2 Theta d-spacing
100 .times. I/I.sub.o
______________________________________
7.78 11.37 28
8.06 10.97 84
8.72 10.14 29
12.62 7.01 8
13.74 6.45 4
15.32 5.67 19
15.98 5.55 22
17.04 5.20 5
17.94 4.95 13
19.16 4.632 100
19.68 4.511 33
20.22 4.392 6
20.50 4.332 26
21.28 4.175 8
21.70 4.096 22
21.94 4.051 13
22.44 3.962 5
23.40 3.802 14
23.76 3.745 36
24.44 3.642 22
25.12 3.545 34
25.58 3.483 42
25.70 3.463 25
26.26 3.394 15
27.02 3.300 20
27.64 3.227 11
28.48 3.134 13
31.04 2.881 5
33.66 2.663 10
______________________________________
Example 6
Preparation of Aluminosilicate SSZ-44 Starting SiO.sub.2 /Al.sub.2 O.sub.3
=50
The reaction described in Example 2 was repeated, with the exception that
0.058 gram of Reheis F2000 was used. This resulted in a starting SiO.sub.2
/Al.sub.2 O.sub.3 mole ratio of 50. After 11 days at 170.degree. C. and 43
rpm a product was isolated and determined by XRD to be SSZ-44. The product
was analyzed and found to have a SiO.sub.2 /Al.sub.2 O.sub.3 mole ratio of
51.
Example 7
Preparation of Aluminosilicate SSZ-44 Starting SiO.sub.2 /Al.sub.2 O.sub.3
=40
The reaction described in Example 2 was repeated, with the exception that
0.073 gram of Reheis F2000 was used. This resulted in a starting SiO.sub.2
/Al.sub.2 O.sub.3 mole ratio of 40. After 11 days at 170.degree. C. and 43
rpm a product was isolated and determined by XRD to be SSZ-44. Analysis of
this product gave a SiO.sub.2 /Al.sub.2 O.sub.3 mole ratio of 38.
Example 8
Preparation of Borosilicate SSZ-44 Starting SiO.sub.2 /B.sub.2 O.sub.3 =50
Three mmol of a solution of Template A (5.33 grams, 0.562 mmol OH.sup.- /g)
were mixed with 1.2 grams of 1.0N NaOH and 5.4 grams of water. Sodium
borate decahydrate (0.057 gram) was added to this solution and stirred
until all of the solids had dissolved. Cabosil M-5 fumed silica (0.92
gram) was then added to the solution and the resulting mixture was heated
at 160.degree. C. and rotated at 43 rpm for 14 days. A settled product
resulted, which was filtered, washed, dried and determined by XRD to be
SSZ-44. The product was found to have a SiO.sub.2 /B.sub.2 O.sub.3 mole
ratio of 63. The X-ray diffraction pattern representative of the as-made
material is tabulated in Table V below.
TABLE V
______________________________________
2Theta d 100 .times. I/I.sub.o
______________________________________
7.72 11.44 33.9
8.03 11.00 81.0
8.70 10.15 37.5
12.61 7.01 10.7
15.33 5.78 20.7
15.96 5.55 25.2
17.02 5.20 6.8
17.91 4.95 16.4
19.16 4.63 100.0
19.71 4.50 6.1
20.51 4.32 36.2
21.24 4.18 7.1
21.67 4.10 30.0
21.98 4.04 13.2
22.46 3.96 6.6
23.40 3.80 11.7
23.51 3.78 10.5
23.80 3.74 37.0
24.42 3.64 23.6
24.73 3.60 19.3
24.88 3.58 23.1
25.13 3.54 37.0
25.58 3.48 37.7
25.70 2.36 19.7
26.24 3.39 20.5
27.02 3.30 25.2
27.66 3.22 10.9
27.96 3.19 4.8
28.55 3.12 15.1
28.92 3.08 4.4
29.62 3.01 11.2
29.85 2.99 7.7
31.08 2.87 6.0
31.95 2.80 5.3
33.73 2.65 8.7
34.87 2.57 9.2
35.57 2.52 4.5
______________________________________
Example 9
Preparation of All-Silica SSZ-44
Three mmoles of a solution of Template A (5.24 g, 0.572 mmol OH.sup.- /g)
was mixed with 0.75 gram of 1.0N KOH and 5.87 grams of water. Cabosil M-5
fumed silica (0.92 gram) was then added to the solution, followed by 0.005
gram of SSZ-44 seed crystals, and the resulting mixture was heated at
150.degree. C. for 31 days. The resulting settled product was filtered,
washed and dried and determined by XRD to be SSZ-44 with a trace amount of
layered material.
Example 10
Calcination of SSZ-44
The material from Example 5 was calcined in the following manner. A thin
bed of material was heated in a muffle furnace from room temperature to
120.degree. C. at a rate of 1.degree. C. per minute and held at
120.degree. C. for three hours. The temperature was then ramped up to
540.degree. C. at the same rate and held at this temperature for 5 hours,
after which it was increased to 594.degree. C. and held there for another
5 hours. A 50/50 mixture of air and nitrogen was passed over the zeolite
at a rate of 20 standard cubic feet per minute during heating.
Representative XRD data for the calcined product is given in Table VI
below.
TABLE VI
______________________________________
2Theta d-spacing
100 .times. I/I.sub.o
______________________________________
7.72 11.45 40
8.06 10.97 100
8.68 10.19 44
11.14 7.94 4
12.00 7.37 6
12.66 6.99 11
13.74 6.44 11
15.32 5.78 4
15.92 5.57 4
17.10 5.18 3
17.96 4.94 5
19.22 4.618 45
19.72 4.502 13
20.54 4.324 10
21.32 4.168 3
21.68 4.099 8
22.00 4.041 5
22.38 3.973 3
23.78 3.742 17
25.20 3.534 10
25.62 3.477 19
27.16 3.284 10
27.70 3.221 7
28.52 3.130 6
28.92 3.087 5
31.10 2.876 4
32.72 2.737 3
33.66 2.663 4
35.00 2.564 5
______________________________________
Example 11
Calcination of B-SSZ-44
The procedure described in Example 10 was followed with the exception that
the calcination was performed under a nitrogen atmosphere.
Example 12
N.sub.2 Micropore Volume
The product of Example 10 was subjected to a surface area and micropore
volume analysis using N.sub.2 as adsorbate and via the BET method. The
surface area of the zeolitic material was 430 M.sup.2 /g and the micropore
volume was 0.185 cc/g, thus exhibiting considerable void volume.
Example 13
NH.sub.4 Exchange
Ion exchange of calcined SSZ-44 material (prepared in Example 10) was
performed using NH.sub.4 NO.sub.3 to convert the zeolite from its Na.sup.+
form to the NH.sub.4.sup.+ form, and, ultimately, the H.sup.+ form.
Typically, the same mass of NH.sub.4 NO.sub.3 as zeolite was slurried in
water at a ratio of 25-50:1 water to zeolite. The exchange solution was
heated at 95.degree. C. for 2 hours and then filtered. This procedure can
be repeated up to three times. Following the final exchange, the zeolite
was washed several times with water and dried. This NH.sub.4.sup.+ form
of SSZ-44 can then be converted to the H.sup.+ form by calcination (as
described in Example 10) to 540.degree. C.
Example 14
NH.sub.4 -Exchange of B-SSZ-44
The procedure described in Example 13 for ion exchange was followed with
the exception that NH.sub.4 OAc was used in place of the NH.sub.4
NO.sub.3.
Example 15
Constraint Index Determination
The hydrogen form of the zeolite of Example 7 (after treatment according to
Examples 10 and 13) was pelletized at 2-3 KPSI, crushed and meshed to
20-40, and then >0.50 gram was calcined at about 540.degree. C. in air for
four hours and cooled in a desiccator. 0.50 Gram was packed into a 3/8
inch stainless steel tube with alundum on both sides of the zeolite bed. A
Lindburg furnace was used to heat the reactor tube. Helium was introduced
into the reactor tube at 10 cc/min. and at atmospheric pressure. The
reactor was heated to about 315.degree. C., and a 50/50 (w/w) feed of
n-hexane and 3-methylpentane was introduced into the reactor at a rate of
8 ml/min. Feed delivery was made via a Brownlee pump. Direct sampling into
a gas chromatograph began after 10 minutes of feed introduction. The
Constraint Index value was calculated from the gas chromatographic data
using methods known in the art, and was found to be 0.2.
At 315.degree. C. and 40 minutes on-stream, feed conversion was greater
than 85%. After 430 minutes, conversion was still greater than 60%.
It can be seen that SSZ-44 has very high cracking activity, indicative of
strongly acidic sites. In addition, the low fouling rate indicates that
this catalyst has good stability. The low C.I. of 0.2 shows a preference
for cracking the branched alkane (3-methylpentane) over the linear
n-hexane, which is behavior typical of large-pore zeolites.
Example 16
Use of SSZ-44 To Convert Methanol
The hydrogen form of the zeolite of Example 6 (after treatment according to
Examples 10 and 13) was pelletized at 2-3 KPSI, then crushed and meshed to
20-40. 0.50 Gram was loaded into a 3/8 inch stainless steel reactor tube
with alundum on the side of the zeolite bed where the feed was introduced.
The reactor was heated in a Lindberg furnace to 1000.degree. F. for 3
hours in air, and then the temperature was reduced to 400.degree. C. in a
stream of nitrogen at 20 cc/min. A 22.1% methanol feed (22.1 g
methanol/77.9 g water) was introduced into the reactor at a rate of 1.31
cc/hr. The conversion at 10 minutes was 100%, and after 11 hours was still
greater than 95%.
SSZ-44 makes very little light gas and produces considerable liquid product
under these conditions. A large proportion of product is due to the
formation of durenes, penta- and hexamethylbenzene (see Table C below).
Formation of penta- and hexamethylbenzene is again indicative of a large
pore zeolite, as the equilibrium diameter of the latter is 7.1 Angstroms
(Chang, C. D., "Methanol to Hydrocarbons", Marcel Dekker, 1983).
TABLE C
______________________________________
Product Wt %
______________________________________
Light gases 2
Xylenes 4
C.sub.9 aromatics 13
C.sub.10 aromatics
34
Pentamethylbenzene
24
Hexamethylbenzene 4
Other C.sub.10+ aromatics
19
______________________________________
Example 17
Pd Exchange
1.0 Gram of calcined and ammonium-exchanged SSZ-44 (made as described in
Example 2) was added to 10.0 grams of water and 1.0 gram of a 0.148M
NH.sub.4 OH solution to give a solution buffered at pH 9.5. Approximately
0.5 wt % Pd was loaded onto the zeolite by ion exchange using a 0.05M
Pd(NH.sub.3).sub.4.2NO.sub.3 solution. The mixture was stirred at room
temperature for 16 hours. The solids were filtered and washed with 1 liter
of water, dried, and calcined to about 482.degree. C. in air for three
hours.
Example 18
n-C.sub.16 Conversion--Hydrocracking
The product of Example 17 was heated at 650.degree. F. in one atmosphere of
hydrogen for two hours. The product was then tested for its activity as a
component in hydrocracking. 0.5 Gram of catalyst was used for the test
which consisted of running 1 mL/hour of n-hexadecane feed with 160
mL/minute of H.sub.2 under the following conditions:
______________________________________
Temp 650.degree. F.
WHSV 1.55
PSIG 1200
______________________________________
The results of the test are shown below.
______________________________________
nC.sub.16 Conversion
97%
Isomerization selectivity
28%
Cracking selectivity
72%
nC.sub.16 cracking conversion
70%
C.sub.5+ /C.sub.4 3.3
C.sub.4 i/n 1.3
C.sub.5 i/n 1.7
C.sub.6 i/n 1.8
______________________________________
As shown above with the nC.sub.16 test feed, SSZ-44 can be used as a
hydrocracking catalyst.
Example 19
Pt-B-SSZ-44
One gram of calcined and ammonium-exchanged B-SSZ-44 (prepared as described
in Examples 8, 11 and 14) was added to 10.0 grams of water and 1.0 gram of
a 0.148M NH.sub.4 OH solution to give a solution buffered at about pH 9.5.
Approximately 0.5 wt % Pt was loaded onto the zeolite by ion exchange
using a 0.05M Pt(NH.sub.3).sub.4 (NO.sub.3).sub.2 solution. The mixture
was stirred at room temperature overnight. The solids were filtered and
washed with 1 liter of water, dried, and calcined to 288.degree. C. in air
for 3 hours.
Example 20
Constraint Index and Activity of Pt-B-SSZ-44
The product from Example 19 was pelleted at 2-3 KPSI, crushed and meshed to
20-40. Then 0.50 gram was dried at 400.degree. F. in air for 4 hours and
cooled in a desiccator. 0.47 Gram was packed in the center of a 3/8 inch
stainless steel tube with alundum on both sides of the zeolite bed. A
Lindburg furnace was used to heat the reactor tube. Helium was introduced
into the reactor tube at 9.4 cc/min. and atmospheric pressure. The reactor
was taken to 800.degree. F., and a 50/50 (w/w) feed of n-hexane and
3-methylpentane was introduced into the reactor at a rate of 10 .mu.l/min.
Feed delivery was made via a piston pump. Direct sampling onto a gas
chromatograph began after introduction of the feed. The constraint index
value was calculated from gas chromatographic data using methods known in
the art, and found to be 1.9.
______________________________________
10 Minutes
40 Minutes
______________________________________
Feed conversion, %
15.4 12.0
Prod. Selectivities
C.sub.6 Isomerization
6.9 6.3
C.sub.5- Cracking
13.1 9.2
Aromatization 6.9 4.9
Dehydrogenation 54.5 60.0
______________________________________
Top